FSBM recombinant protein

ABSTRACT

The invention discloses a FSBM recombinant protein for conferring protection against group C streptococcus infection in an animal subject, comprising: a first peptide fragment, having an amino acid sequence set forth as SEQ ID NO. 5; a second peptide fragment, having an amino acid sequence set forth as SEQ ID NO. 6; a third peptide fragment, having an amino acid sequence set forth as SEQ ID NO. 7; and a fourth peptide fragment, having an amino acid sequence set forth as SEQ ID NO. 8. The invention also discloses a method of protecting an animal subject against group C streptococcus infection.

CROSS REFERENCE TO RELATED APPLICATIONS

The application claims the benefit of Taiwan application serial No. 105142098, filed Dec. 19, 2016, the subject matter of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a FSBM recombinant protein, and more particularly, to a FSBM recombinant protein for conferring protection against group C streptococcus infection in an animal subject.

2. Description of the Related Art

Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes. Cell division in this genus occurs along a single axis in these bacterial, thus they grow in chains or pairs; and therefore are named as Streptococcus.

Group B streptococcus and group C streptococcus are the main pathogens causing streptococcus infection in poultry and livestock. As an example, group C streptococcus infection may cause strangles in horses, as well as septic streptococcus infection in sheep and pig.

Clinically, antibiotics such as penicillin G and cephalosporin can be used to treat group C streptococcus infection. However, excess use of antibiotics is not only the reason of allergy in consumer of animal by-products, but also the factor contributing to emergence of drug-resistant pathogens. In light of this, it is necessary to provide a vaccine for conferring protection against group C streptococcus infection in an animal subject.

SUMMARY OF THE INVENTION

It is therefore the objective of this invention to provide a FSBM recombinant protein for conferring protection against group C streptococcus infection in an animal subject.

One embodiment of the invention discloses a FSBM recombinant protein or conferring protection against group C streptococcus infection in an animal subject. The FSBM recombinant protein comprises a first peptide fragment, having an amino acid sequence set forth as SEQ ID NO. 5; a second peptide fragment, having an amino acid sequence set forth as SEQ ID NO. 6; a third peptide fragment, having an amino acid sequence set forth as SEQ ID NO. 7; and a fourth peptide fragment, having an amino acid sequence set forth as SEQ ID NO. 8. Preferably, the FSBM recombinant protein has an amino acid sequence set forth as SEQ ID NO. 10.

Another embodiment of the invention discloses a method of protecting an animal subject against group C streptococcus infection by immunizing the animal subject with said FSBM recombinant protein to facilitate production of antibody against group C streptococcus in the animal subject.

In a preferred form shown, the FSBM recombinant protein is immunized the animal subject by either intramuscular injection or subcutaneous injection.

In a preferred form shown, the FSBM recombinant protein is immunized the animal subject in a dosage of 1 mg/kg of the animal subject once in 7 days.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinafter and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1a depicts the SDS-PAGE analysis of the FSBM recombinant protein according to the present invention.

FIG. 1b depicts the Western blotting analysis of the FSBM recombinant protein according to the present invention by the anti-SPE B mouse serum.

FIG. 1c depicts the ELISA analysis of the FSBM recombinant protein according to the present invention by the anti-SPE B mouse serum.

FIG. 2 depicts the survival rate analysis of the FSBM recombinant protein according to the present invention-immunized mice which are challenged with group C streptococcus.

FIG. 3a depicts the SDS-PAGE analysis of the porcine cardiac myosin.

FIG. 3b depicts the Western blotting analysis of the porcine cardiac myosin by the FSBM recombinant protein-immunized serum.

In the various figures of the drawings, the same numerals designate the same or similar parts. Furthermore, when the term “first”, “second”, “third”, “fourth” and similar terms are used hereinafter, it should be understood that these terms refer only to the structure shown in the drawings as it would appear to a person viewing the drawings, and are utilized only to facilitate describing the invention.

DETAILED DESCRIPTION OF THE INVENTION

A FSBM recombinant protein according to the present invention comprises a first peptide fragment, a second peptide fragment, a third peptide fragment and a fourth peptide fragment. The first peptide fragment is derived from a partial fragment of the FnBR domain of Sfb1 (one of the fibronectin-binding proteins), the second peptide fragment is derived from a partial fragment of the immunogenic domain of SLS (streptolysin S), the third peptide fragment is derived from a partial fragment of the C3-binding motif of SPE B (streptococcal pyrogenic exotoxin B), and the fourth peptide fragment is derived from a partial fragment of the C-terminal conserved segment of M protein.

The FSBM recombinant protein can be expressed by E. coli cells. As an example, an expression plasmid for expressing the FSBM recombinant protein can be constructed and transformed into the E. coli cells. The FSBM recombinant protein expressed by the E. coli cells can be purified, and the purified FSBM recombinant protein can therefore be obtained.

Specifically, the expression plasmid comprises a first DNA fragment corresponding to the first peptide fragment, a second DNA fragment corresponding to the second peptide fragment, a third DNA fragment corresponding to the third peptide fragment and a fourth DNA fragment corresponding to the fourth peptide fragment. Moreover, the first, second, third and fourth DNA fragments preferably have the codon usage of E. coli, thus the E. coli cells can show preferable expression efficiency. In this embodiment, the first, second, third and fourth DNA fragments have nucleic acid sequences set forth as SEQ ID NOS: 1, 2, 3 and 4, respectively. In addition, the first, second, third and fourth peptide fragments expressed by the E. coli cells have the amino acid sequences set forth as SEQ ID NOS: 5, 6, 7 and 8, respectively.

Furthermore, a linker fragment can be added between the first and second DNA fragments, the second and third DNA fragments, and the third and fourth DNA fragments. The sequence of the linker fragment can be appreciated by a person having ordinary skill in the art; and therefore detail description is not given to avoid redundancy. In this embodiment, the expression plasmid comprises a nucleic acid sequence set forth as SEQ ID NO: 9, while the FSBM recombinant protein expressed by the E. coli cells has an amino acid sequence set forth as SEQ ID NO: 10.

The construction of the expression plasmid is the prior art well-known in the field; and therefore is not limited to the following statement. In this embodiment, the DNA fragment with the nucleic acid sequence set forth as SEQ ID NO: 9 is synthesized and digested by the restriction enzyme. The digested DNA fragment is then ligated to a pET-24a vector by a ligase, and the expression plasmid is obtained.

In this embodiment, after the expression plasmid is transformed into the E. coli BL21(DE) pLysS, the E. coli BL21(DE) pLysS can express the fusion protein with 6×His tag by IPTG induction. The FSBM recombinant protein can be then purified using Ni²⁺ chelating chromatography.

The purified FSBM recombinant protein can be used to immunize an animal subject to induce production of an antibody against group C streptococcus, conferring protection against group C streptococcus infection in the animal subject. As an example, the FSBM recombinant protein can be immunized the animal subject in a dosage of 1 mg/kg of the animal subject once in 7 days for 3 times by either intramuscular injection (IM injection) or subcutaneous injection (SC injection).

Moreover, a pharmaceutically-acceptable adjuvant can be mixed with the purified FSBM recombinant protein to form a group C streptococcus vaccine. The pharmaceutically-acceptable adjuvant can improve the stability of the FSBM recombinant protein in the animal subject. Alternatively, the pharmaceutically-acceptable adjuvant can enhance immune responses of the FSBM recombinant protein; and therefore the FSBM recombinant protein have a preferable effect on inducing the production of the antibody against group C streptococcus. Specifically, the pharmaceutically-acceptable adjuvant can be an oil-based adjuvant or an oil-in-water adjuvant. As an example, the oil-based adjuvant can be complete Freund's adjuvant (CFA) or incomplete Freund's adjuvant (IFA), and the oil-in-water adjuvant can be AddaVax™.

To validate the FSBM recombinant protein according to the present invention can be used to immunize the animal subject to induce the production of the antibody against group C streptococcus and to protect the animal subject from death due to group C streptococcus infection, the following trials are carried out.

Trial (A).

In trial (A), the expression plasmid is transformed into the E. coli BL21(DE)pLysS cells. The FSBM recombinant protein is expressed by 0.5 mM IPTG and purified using Ni²⁺ chelating chromatography. The purified FSBM recombinant protein is examined by SDS-PAGE. As shown in FIG. 1a , the FSBM recombinant protein (group A1) has a molecular weight of about 18 kDa.

The purified FSBM recombinant protein is further analyzed by Western blotting and ELISA using the anti-SPE B mouse serum. As shown in FIGS. 1b and 1c , the FSBM recombinant protein (group A1) can be recognized by the anti-SPE B mouse serum.

Trial (B).

In trial (B), the BALB/c mice are immunized with the FSBM recombinant protein (25 μg) combined with equal volume of the pharmaceutically-acceptable adjuvant by intraperitioneal injection (once in 7 days for 3 times). On day 28^(st) (7 days after the 3^(rd) immunization), the BALB/c mice are challenged with group C streptococcus (9×10⁸ CFU, ATCC 43078) by intraperitioneal injection. The survival rate of the BALB/c mice infected by group C streptococcus is recorded. As shown in FIG. 2, all of the BALB/c mice without immunizing with the FSBM recombinant protein (group B0) die on day 2^(nd), and all of the BALB/c mice with immunizing with the FSBM recombinant protein (group B1) survive until day 14^(th) (survival rate 100%). That is, the FSBM recombinant protein according to the present invention can effectively induce the production of the antibody against group C streptococcus, protecting the animal subjects from death due to group C streptococcus infection.

Trial (C).

In trial (C), the serum collected from the BALB/c mice immunized with the FSBM recombinant protein are used. Referring to FIGS. 3a and 3b , the FSBM recombinant protein-immunized serum can recognize the FSBM recombinant protein (group C2), but not the porcine cardiac myosin (group C1), showing that immunization the animal subject with the FSBM recombinant protein according to the present invention will neither induce autoimmune response against cardiac tissues nor cause rheumatic heart disease.

Accordingly, immunizing the animal subject with the FSBM recombinant protein sufficiently facilitate production of antibody against group C streptococcus in the animal subject. With such performance, the animal subject shows a decreased risk of infection by group C streptococcus, as well as a reduced risk of dying due to group C streptococcus infection.

Although the invention has been described in detail with reference to its presently preferable embodiment, it will be understood by one of ordinary skill in the art that various modifications can be made without departing from the spirit and the scope of the invention, as set forth in the appended claims. 

What is claimed is:
 1. A FSBM recombinant protein for conferring protection against group C streptococcus infection in an animal subject, comprising: a first peptide fragment, having the amino acid sequence set forth in SEQ ID NO. 5; a second peptide fragment, having the amino acid sequence set forth in SEQ ID NO. 6; a third peptide fragment, having the amino acid sequence set forth in SEQ ID NO. 7; and a fourth peptide fragment, having the amino acid sequence set forth in SEQ ID NO.
 8. 2. The FSBM recombinant protein as claimed in claim 1, wherein the FSBM recombinant protein has the amino acid sequence set forth in SEQ ID NO.
 10. 3. A method of protecting an animal subject against group C streptococcus infection by immunizing the animal subject with the FSBM recombinant protein as claimed in claim 1 to facilitate production of antibody against group C streptococcus in the animal subject.
 4. The method as claimed in claim 3, wherein the FSBM recombinant protein is administered by intramuscular injection or subcutaneous injection.
 5. The method as claimed in claim 4, wherein the FSBM recombinant protein is administered to the animal subject in a dosage of 1 mg/kg of the animal subject once in 7 days. 